Mammalian Sugar Transporters:Their Localization and Link to Cellular Functions.

Abstract

Sugar transporters are integral membrane proteins that transport sugars across cellular membranes. Recent advances in molecular biology have revealed two major families of them: the Na+-dependent glucose transporter (SGLT) family, and the facilitated-diffusion glucose transporter (GLUT) family. At least three isoforms of SGLT and six of GLUT have been identified so far. Expression of specific isoforms depends on the type of cell, tissue, or organ, and the physiological and pathological conditions. Their precise localization at the specific domain (s) of the plasma membrane or in the intracellular organelles is closely related to their cellular functions. In this review, their localization and link to specific cellular functions are addressed in the following cases: active transepithelial transport of glucose; glucose transport in blood-tissue barriers; possible role of glucose transporter and the gap junction in the transepithelial transport of glucose; the contribution of glucose transporters in the regulation of blood glucose level; and localization of glucose transporters at specific plasma membrane domains.